Method of making a fire resistant laminated fabric



Patented Dec. 7, 1948 METHOD OF MAKING A FIRE RESISTANT LAMINATED FABRIC Zachary T. Walter, Los Angeles, Calif.

No Drawing. Application August 4, 1944,

Serial No. 548,148

4 Claims. 1

My invention relates to the production of laminated products having unusually high resistance to fire.

Plastic products composed of laminae of woven or porous fabrics impregnated with cellulosic materials, while having many highly desirable characteristics, have not been generally successful for use where there is any substantial fire hazard due to the fact that the cellulosic materials themselves are not fire resistant to any marked degree,

and when used to impregnate fabric, the strands of the fabric substantially increase the combustibility since they provide a wicking for the flame and increase the afterglow. Attempts have been made to render such products more fire resistant by admixing various fireprooflng agents with the impregnating compound, but those attempts have been unsuccessful in that there is an objectionable reaction between the fireprooflng and impregnating compounds which tends to decomposition and to prohibit the obtaining of a proper bond between laminae.

Heretofore I have obtained substantially improved results by a method disclosed in my copending application Serial No. 547,639, filed August 1, 1944, now abandoned, wherein I produce a concentration of triphenylphosphate around the fabric fibres by pretreating the fabric with the triphenylphosphate, but in so doing I had considered. it necessary to utilize a fireproofing agent which was compatible with the cellulosic compound in order to obtain a proper bond and in order to avoid too pronounced a stratification. The result was, therefore, that in subsequently applying the cellulosic impregnating solution to the fabric so pretreated with the triphenylphosphate, their triphenylphosphate became somewhat dispersed in the impregnating solution, reducing the concentration of the fireproofing agent around the fabric fibres.

I have found that I can overcome those difliculties by first pretreating the fabric with a chlorinated parafline solution and allowing the pretreated fabric to cure so as to provide an impregnated laminating sheet; and then I carry out thelamlnating by brush or spray coating the successive pretreated sheets with a volatile cellulosic compound which is incompatible with the chlorinated parafhne, but carrying a solvent which will soften the chlorinated parafline, so that the cellulosic solution is carried into the fabric interstices and becomes bonded to the chlorinated parafilne which immediately encases the fibres, without dispersing the chlorinated parafllne. n this manner the concentration of the fireproofing agent around the fabric is not destroyed or reduced. Moreover there is no detectable shrinkage of the pretreated sheet as would be the case with an untreated sheet orwith a sheet pretreated with a compatible fireproofing agent, and the moisture absorption of the product is reduced to a minimum. It is, therefore, to those purposes and advantages that my present invention is devoted. I

In a preferred example of my present invention, I first pretreat the fabric sheets to be used in producing the laminated product. A wide range of fabric sheets may be used such, for instance, as burlap, cotton batting, or osnaburg. For this pretreating I use a chlorinated paraifinc whose percentage of chlorine is 68-72%, the chlorinated paraffine being first dissolved in acetone or in a suitable mixture of aromatic hydrocarbon solvents such as benzene and toluene.

The pretreating is efiected by thoroughly impregnating the fabric with this volatile solution,

preferably immersing the fabric in the solution.

The preferred concentration should be such that the impregnating material carried by the fabric is equal to the weight of the fabric. All the volatiles of the solvents are then evaporated or released from the fabric sheets, after which the sheets will be somewhat rigid but will still possess sufficient flexibility and extensibility to be stretched onto a male mold in conforming relationship thereto, even though the mold may have reverse curves and the like. After the thus pretreated sheets have cured, the release of the solvents leaves the chlorinated paraffine encasing the fibres and strands with interstices between the strands.

Then after coating the mold with a suitable mold release agent, I brush or spray coat the mold with a coating of the adhesive laminating solution to be described. For the latter I form a volatile solution consisting, by weight, of 70% cellulose acetate, 18% triphenylphosphate, and 12% dibutyl phthalate, or other phthalate plasticizer compatible with cellulose acetate and triphenylphosphate, dissolved in a solvent, such as one comprised of acetone and 10% ethanol, by volume. vSuch a laminating solution is incompatible with the chlorinated paraffine, although the solvents will dissolve the latter.

While this moldcoat is wet, I stretch thereon one of the pretreated sheets of fabric, the coating causing the pretreated sheet to suitably conform and adhere to the mold. After allowing the applied sheet to preliminarily cure until most of the solvents from the coating are released, I

brush or spray coat the outer surface of the applied sheet with another coating of the laminating solution. To obtain a final product having great monolithic characteristics, Iallow the lastmentioned coating to cure until it is in a nontacky gel state-that is, it is pliant and moldable but is not tacky-and then press the coating into the sheet by using a spatula or other pressureapplying means, which forces columns of the pliant coating into the interstices in the fabric. I then allow the coating to further preliminarily cure until most of its solvents are released. I may omit the pressing operation if a product of less monolithic nature is suitable. The preliminary curing of the applied coating requires about twenty minutes in a-70-80 atmosphere of below 50% relative humidity.

Next, I apply another brush or spray coat of the laminating solution over the last-mentioned coat, and while it is still wet I superimpose thereon another of the pretreated fabric sheets and repeat the procedure above described. The described series of steps are repeated until a final product having the desired number of laminae is obtained. After thus completing the laminating, the article is stripped from the mold and cured or dried until all' solvents have been released.

Inasmuch as, by using my pretreated sheets, there is no shrinkage of the sheets during the laminating, it is unnecessary to allow for such shrinkage when a. final product of meticulous dimensions is desired.

Severe flame tests on a product formed in accordance with my present invention show the product to possess substantially greater resistance to flame than any other laminated product containing cellulose of which I am aware. The composite product possesses greater fire resistance than do the pretreated sheets when tested separately. The fireproofing agent, being incompatible with the cellulose acetate solution, remains concentrated around the fabric fibres, which ordinarily is the area most subject to burning in such a product. The chlorinated parafline being non-brittle, there is no necessity for any additional plasticizing agent around the fabric fibres, while the triphenylphosphate and phthalate suitably plasticize the cellulose acetate I claim:

1. The method of producing a fire-resistant laminated article which comprises impregnating porous fabric sheets with chlorinated paraffine dissolved in a solvent, drying the sheets, then successively combining them in superimposed relation by coating each successive sheet with a volatile solution having cellulose acetate as its base and carrying a solvent for the chlorinated parafline, and laying the next successive sheet thereon while said coating is wet.

2. The method of claim 1 wherein the concentration of chlorinated paraffin provided by the impregnating is equal in weight to the weight of the fabric.

3. The method of claim 1 wherein the chlorinated parafline has a chlorine content of 68-72%.

4. The method of producing a fire-resistant laminated article which consists of impregnating porous fabric sheets with chlorinated parafiin dissolved in a solvent, drying the sheets, and then successively combining them in superimposed relation by coating each successive sheet with a volatile solution having cellulose acetate as its base and carrying a solvent for the chlorinated paraffin, drying said coating to a non-tacky gel state, pressing the coating, while in said state, into the interstices of the coated sheet, finally drying said coating, applying a sec0d coat of the volatile solution to the last-named coat and superimposing the next successive sheet thereon while the last applied coat is wet.

ZACHARY T. WALTER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,246,810 Ellis Nov. 13, 1917 1,523,813 Lindsay Jan. 20, 1925 FOREIGN PATENTS I Number Country 1 Date 379,145 Great Britain Aug. 25, 1932 

